A full duplex radio (FDR) or full duplex communication scheme means a communication scheme for enabling a user equipment to simultaneously perform transmission and reception using the same resource. In this case, the same resource means the same time and frequency. FDR communication or full duplex communication can be referred to as two-way communication.
FIG. 1 is a conceptual diagram illustrating a user equipment (UE) and a base station (BS) that support FDR.
Referring to FIG. 1, there are three types of interferences in a network that supports the FDR. The first one is intra-device self-interference. The intra-device self-interference means that a signal transmitted from a transmit (Tx) antenna of a BS or UE is received by a receive (Rx) antenna of the BS or UE, thereby acting as interference. Since the signal transmitted from the TX antenna is transmitted with high power and a distance between the TX antenna and the RX antenna is relatively short, the signal is received at the RX antenna with almost no power loss. Thus, receive power of the signal is much higher than that of a desired signal. The second one is UE-to-UE inter-link interference. When a network supports the FDR, the UE-to-UE inter-link interference is increased. Specifically, if an uplink signal transmitted by a UE is received by an adjacently located UE, the uplink signal may act as interference to the adjacently located UE. This type of interference is referred to as the UE-to-UE inter-link interference. The third one is BS-to-BS inter-link interference. Similar to the UE-to-UE inter-link interference, the BS-to-BS inter-link interference is also increased when a network supports the FDR. If signals transmitted between BSs or heterogeneous BSs (e.g., pico, femto, relay, etc.) in a HetNet situation are received by an RX antenna of another BS, the signals may act as interference to another BS. This type of interference is referred to as the BS-to-BS inter-link interference.